Wind-up coil



Jan. 17, 1956 M. L. DOELZ WIND-UP COIL Filed April 24, 1952 IN VEN TOR.4412 r1 l 00!; z

Ar razwner WIND-UP COIL Melvin L. Doelz, Glendale, Califi, assignor toCollins Radio Company, Cedar Rapids, Iowa, a corporation of IowaApplication April 24, 1952, Serial No. 284,081

3 Claims. (Cl. 336-15) This invention relates to a variable inductor.

In electronics it is oftentimes desirable to use a variable inductance.Variable inductances may be constructed with a slide contact whichengages a Wound inductance. The contact may be connected electrically toone end of the coil so as to short out those turns between the slidecontact and the end. The remaining turns are the effective ones. Eventhough some of the turns are shorted out, mutual inductance existsbetween them and the active turns.

It is an object of this invention, therefore, to provide means forphysically separating shorted and effective turns of a variableinductance.

Another object of this invention is to provide means for increasing theQ obtainable with a variable inductance.

Yet another object of this invention is found in the provision for arotatably supported coil form about which is wound two portions ofconductors. A pair ofrollers are mounted between the portions.

A feature of this invention is found for coil.

Further objects, features, and advantages of this invention will becomeapparent from the following description and claims when read in view ofthe drawings, in which:

Figure l is a side view of the variable inductance of this invention,and

Figure 2 is a top view of the variable inductance.

Figure 1 shows a base plate 10 which has end plates 11 and 12 mountedthereon. The end plates may be made of insulating material, as forexample, Bakelite.

Rotatably supported between the end plates 11 and 12 is a coil form 13which may be supported by an axle 14. A pair of lead screws 16 and 17,respectively, extend from end plates 11 and 12 parallel to the coil form13 and are rotatably supported in the end plates.

A driving means 18, as for example, an electric motor. is mounted to thebase plate 10 by'stand-oifs 19 and 21 and has an output gear 22. Thecoil form 13 supports a gear 23 which meshes with driving gear 22. Thelead screws 16 and 17 support gears 24 and 26, which mesh with the gear23.

A roller assembly 27 has a pair of threaded projections 23 and 29 thatengage the lead screws 16 and 17, respectively. A pair of rollers 31 and32, respectively, are supported on the member 27 at an angle.

The roller 31 is mounted in a bearing 33, as best shown in Figure 2, andthe roller 32 is mounted in a bearing 34 which is movable in a slot 36formed in the member 27. A spring 37 biases the bearing 34 away from theroller 31.

A flexible conductor 38 is wound about the coil form 13 and has one endattached to a band 39. An output contact 41 is mounted on the plate 11and engages the band 39. The conductor 38 is wound about the coil form13 until it is immediately below the roller 31 and then passes up overthe roller 31 and between a pair of flexible contacts 42 and 43 carriedon the member 27. it then passes over the roller 32 and back around thein the provision means that physically separate two portions of arespectively,

:ited States Patent opposite end of the coil form ductive band 44.

A slide contact 46 is mounted on the end plate 12 and contacts the band44. Extending between end plates 11 and 12 is a conductive rod 47 and aflexible slide contact 48 extends from the member 27 to engage the rod47. The contact 48 is electrically connected to the contacts 42 and 43.

A terminal 49 is connected to the member 47.

In operation, electrical connections are made to contacts 41, 46 and 49.Contacts 49 and 41 might be connected together so as to short out theturns at one end of the coil. The position of the member 27 iscontrolled by the lead screws 16 and 17 which are driven by the motor 22through the gears 23, 24 and 26. The gears 23, 24 and 26 are formed sothat the member 27 moves at the correct speed longitudinally of coilform 13 as the coil form is rotated.

As the coil form is rotated, the number of turns at one side of the coilwill be increased and those at the other side will be decreased. If itis assumed that the contacts 41 and 49 are connected together, thenthose to the left of Figure 1 will be shorted by the member 27 and thoseto the right will be the effective turns.

It is to be noted that the shorted turns are physically separated fromthe active turns by the distance between the outer edges of the rollers31 and 32. As is well known to those skilled in the art, physicalseparation decreases mutual inductance between a pair of coils and thusthe mutual inductance will be substantially less than in a coil wherethe shorted turns are kept immediately adjacent the active coils. Thisresults in an inductance of high inertia and gives a higher Q than isobtained with less physical separation.

Although this invention has been described with respect to a particularembodiment thereof, it is not to be so limited as changes andmodifications may be made therein which are within the full intendedscope of the invention, as defined by the appended claims.

I claim:

1. Apparatus comprising, a base plate, a pair of end plates attached tosaid base plate, a coil form of insulating material rotatably supportedbetween said end plates. a pair of lead screws rotatably supportedbetween said end plates, a roller assembly threadedly supported by thepair of lead screws, a pair of rollers mounted on the roller assembly, aflexible conductor wound about one end of said coil form, passing overthe rollers and wound about the opposite end of said coil form, a firstwiper contact mounted to one end plate and engageable with one end ofsaid flexible conductor, a second wiper conductor attached to the otherend plate and engageable with the opposite end of said coil, 2. thirdwiper contact mounted on said roller assembly and engage-able with saidflexible conductor between the rollers, a driving means connected tosaid coil form and said pair of lead screws, a conducting bar mountedbetween said end plates, and a fourth slide contact extending from saidroller assembly to said conductor bar.

2. A variable inductor comprising, a base plate, a pair of end platesmounted on said base plate, a coil form of insulating material rotatablysupported between said end plates, a pair of lead screws rotatablysupported between said end plates, a roller assembly threadedly receivedon said lead screws, a pair of rollers supported by said roller assemblyso that their planes make an obtuse angle, one of said rollers movabletransversely of said roller assembly and spring biased away from theother roller, a pair of conducting bands attached adjacent opposite endsof said coil form, a flexible conductor attached to one of saidconducting bands and wound about one end of said coil form, saidflexible conductor passing over the first until it connects to aconroller and around the second roller, and then wound about theopposite end of the coil form and connected to the other conductingband, a first Wiper contact mounted on said first end plate andengageable with said first conductive band, a second wiper contactconnected to the other end plate and engageable with the other end band,a third wiper contact mounted to said roller assembly and engageablewith said flexible conductor between said rollers, a conductive shaftextending between said end plates, a fourth wiper contact connected tosaid third wiper contact and engaging said conducting shaft, and adriving means connected to the pair of lead screws and the coil form.

3. Movable carriage means for winding and unwinding a flexible wirereceived on opposite ends of a single rotat'able coil form supported bya frame member comprising, a pair of threaded shafts rotatably supportedadjacent said coil form by said frame, gears fixedly provided on saidcoil form and threaded shafts in meshed relationship to relativelyrotate them with the pitch of said threaded shafts and said wound Wireactuated in the same direction, threaded projections secured to saidcarriage and received on said threaded shafts, a pair of pulleyssupported rotatably at opposite ends of said carriage and each inclinedtoward and receiving said flexible wire, said flexible wire received inan S-form over the outer portions and between said pulleys, a contactfixed on said carriage and slidably contacting the flexible wire as itpasses between said pulleys, and said pulleys spring biased away fromeach other transversely of said coil axis whereby said flexible wire ismaintained taut at all times.

References Cited in'the file of this patent UNITED STATES PATENTS1,642,488 Clausen Sept. 13, 1927 2,037,061 Bliss Apr. 14, 19362,175,554- Bliss Oct. 10, 1939

